One of them seems to predict that Windows 8 will be a flop on desktop PCs, while doing OK in tablets.

As Mary Jo Foley reports, the report says "Windows 8 will be largely irrelevant to the users of traditional PCs, and we expect effectively no upgrade activity from Windows 7 to Windows 8 in that form factor."

That irrelevance may be true in the context of the report, which was about corporate system infrastructure software -- that is, software that helps businesses upgrade or standardize software on the computers they already own.

But as a general statement, it's totally false.

Microsoft hardly EVER sees a lot of upgrades to new versions of Windows on existing PCs. The vast majority of Windows sales come with new PCs instead.

For example, with Windows 7, Microsoft recognized about $850 million in retail sales in the quarter it was released. Overall, Windows made about $5.2 billion in sales that quarter. (It's a little confusing because the reported number, $6.9 billion, includes a deferral from previous quarters.)

In other words, in the quarter Windows 7 was released, almost 75% of the money came from sales on new PCs. That percentage has gone up since then. It usually hovers between 80% and 85%.

Over the next couple of years, enterprises might also cover Windows on their long-term license agreements. But usually they're doing this because it's the only way to get Windows Enterprise Edition -- the most full-featured version of the OS. Not because they plan to upgrade existing computers in place.

Upgrades are a very small part of Microsoft's Windows business.

The real measure of Windows 8's success will be whether it can drive an uptick in PC sales.

That's why Microsoft is putting a lot of attention into the tablet side of Windows 8 -- it hopes that Windows 8 tablets will recapture some consumers who otherwise would have bought an iPad, and stop the slow invasion of iPads into the enterprise.

If Windows 8 fails to affect the PC market at all, and iPads and other tablets keep stealing PC sales, then Windows 8 is a failure from Microsoft's perspective.

But regardless, consumers and businesses will almost certainly still buy hundreds of millions of desktop and laptop PCs over the next three years. Once Windows 8 is released, most of those new PCs will run Windows 8. That's not irrelevant.